Air control mechanism



Nov. 25, 1941.

, w. L. CARLSON 2,263,980 AIR CONTROL MECHANISM n Filed June 16, 1938 2 Sheets-Sheetl l nvenfor attorneys Nov. 25, 1941.

w. L. CARLSON 2,263,980 AIR CONTROL I VIECHANISM Filed June 16, 1938 2 Sheets-Sheet 2 Gttotnegs Patented Nov. 25, 1941 Alfa CGN-moi. MEGHANIsivIv Wilbur Carls'cn, Rochester,

General Mtors G'orporationg- Detroit, f Mich.;- ai' corporationLoii-Delaware Applimeion innere, isssgsriai'N; 214:097"

(omev-itzfl-l 145 Claims;

This invention relates generally to an aircon-l trol mechanismV and-more particularly to amechanism which is adaptedv toV automatically regulate or control the ow of a forced draft of air to the fuel or fire bedoff a mechanicallstoker',

1n the usual types of domestic stokers; it is customary to provide for the.intermittent-feed;l ing of fuel and the supply of air under presfi sure to the fuel bed only duringthezfuelfeedperiod and rely upon. anatural draft to maintain combustion during the intervals between the feedingzperiods; The: frequency and" length of the'feeding: periods are. generallyv con trolled primarilyin accordance With the` vary; ing demands for heat with means. to also pro` vide for intermittent operation at predeterminedintervals to maintain combustionA when thereis no demand for heat.

Under such varying conditions of operation'as are set forth above, it will be apparent-that thereY may be considerable variation in the thicknessof the fuel bed and theV amount ofresistance which is offered thereby to the air flow through the bed, and to assure sufficient air to obtain proper combustion when the fuel bed is` thick and prevent excessive draft when the fuel bed; is thin, it hasV been found desirabled to prev-ide some means to regulate the airy flowin accordi-v ance with the resistance offered bythe fuelbed.`

It has also been determined that' there iszboth:

a predetermined thickness of fuel bed and. al certain ratev of combustion with` af definite re-A lation between the fuel and air feed which will provide the maximum efficiency during, the operating periods ofthe Stoker. Althoughf this predetermined thickness of the fuelbed. cannot' be constantly maintained because ofthe vary ing conditions of operation, it has been foundr that such thickness maybe obtained duringithe fuel and air feeding. periods by so'controlling or regulating the air supply. that anlexcess volume of air is provided' when the bed is too thickto increase the rate of combustion'andthereby,` reduce the thickness of theI fuel bed and a deficient volume of airis provided when the-bed is too thin to reduce the rate-of combustionandl thereby increase the thickness of the fuel'bed.

The principal object' of the presentiinvention is the provision of a mechanismvvhich will automatically regulate or control the flow of a forced draft of air to the fuel bed of a mechanical stoker.

A further object of theinvention-is to-provide such a mechanism as will regulatev theair sistance offeredf the fuel bedland function as described above: to obtain; and maintainv apredeterminedlthickne'ssof: the fuelrbed within praeticalnlimitsl` 'Y n y* A further -V object is to:` providesucha mechanism. in the. form. ofA ai self-adjusting= damperplaced"v in the air' delivery. ductextending`v from the o l-ltlet'of4v the forced draftfanorblower to the fuel-bed, and vvhichmis.v so constructed and mountedY asa to. automatically regulate the air flow to the fuel.y bedginthe. desired manner.

A. still further.Y object is'tof provide a self-ad iusting damper of this. character-Winch incorporatesmanually.` operable. adjusting means4 to permit adjustment ofthe automatic operating characteristics and adjustmentcf the rangeiof operation 13o-compensate; forvariations *inl the quality of' the. fuel or changes inithefrateof fuel eld:A

OtherY objects,4 andthe f advantages .of Vthe pres.- entrinven'tion will be apparent Vfrom-thefollowing: description of. anembodiment thereof which. is,v illustrated inthe accompanying; drawings in.

which.:` e l i igure 1 isa-diagrammatic side elevation; with parts in section, of a furnace provided.- withv astoker embodying they present` invention.

Figure 2- is alongitudinal cross1 section, withV partsin elevation, of lthe Stoker air ductl andthe: self-adjusting,- damper.

Figure 3 is. aitransverse1 cross section on the' line 3-v-3'of Figure 2;

Figure 4` is. a sidev elevationv of the air duct showing an adjustingr meansvffor` the dampen Figur-'e5 is-a side-elevation of a portion of the ain ductvvith part of the wall broken-away'to.- illustrate the damper in vside elevation, f

Referring first to Eigure 1 for a diagram-4 matic. showing i of y one application of the invention, .a furnace IfY is shown-assprovidedfwithan underfeed stoker 21. which is adapted tofeed r fuel- The air for combustion f is supplied by a duct4 5 connectedto-av forced draftffan or blower 6; to` anair chamber 1- andto. the fuel-bedthrough, the. ports v. 8l-

Theair control4 mechanism-*Which isfthe sub-- ject-of the-,present invention includes thedamper indicated generally at 9 Whichis located in the air: ductlvintermediate `the lblower 6 andthe air chamber Y 1 andwhich is. constructed and arranged in the manner now to. bev described in detail.

` The damper. is inthefnature of `a-vafn'e which 'lovv automatically in accordance with the reeAv 55'" is formed` ofl sheet metal tothe configuration shown 'in Figures 2 and 5 with a substantially at upper surface I and a curved lower surface of said strap riveted to the damper and the other;

end riveted to the plate.

The curved jacent one end on the shaft I 4 ,extending between the side walls of the air duct 51andis suppo'rted a cam I5 fixed on the adjacent its other end by shaft I6 which also extends between the side walls of the air duct. 'Ihe shaft I6 is formed with a squared portion of the side walls to provide for the connection thereto of a handle II- by means Vof which thel shaft I 6 and cam I5 may be rotated to adjust the position of the plate I2 about the pivot shaft I4. 'Ihe handle II is formed with a pointer operating over a graduated indicating scale I8 on a plate I9 secured to 'the sidewall ofthe air duct, and any known means may be provided to hold the handle at any desired point of adjustment such as the means indicated in Figure 4 which consists of a bolt extending through the handle I'I and an arcuate slot 2| in the plate I9 with its head positioned between the plate I 9 and the adjacent side wall of the air duct 5 and with a wing nut 22 on said bolt whereby the handle I'I may be frictionally secured to the plate I9.-

At one end, ther damperisbent downwardly to provide a transverse depending curved'wall 23 andY associated therewith isa depending curved wall 24 on the sheet metal plate 25 which isv secured to the upper wall of the air duct 5. This wall 24 is formed with a V-shaped notch 26 and during movement of the damper on the curved fulcrum plate I2, the wall 23 moves closely'adjacent to the wall 24 and functions as a valve controlling the passage of air through the V-shaped notch for a purpose to be hereinafter described.

Adjacent this end, the damper is also formed with a depending ear orlug 21 having an opening to receive the spring 28 which extends diagonally downwardly through a slot in the strap I3 andan opening in the plate I2 as shown in Figure 2.v The lowerA end of the spring 28 engages with a" screwthreaded stud 29 which extends through an opening in an angularly offset portion of the bottom wall of the air duct 5 and is provided exteriorly thereof with the nut 30 to afford manual adjustment of the spring tension.

The opposite end ofthe damper is provided' with `an extension in the form of a plate 3I which is adapted to be engaged by a weight 32 which slides vertically onthe guide rod 33 extendingl between the upper and lower walls of the air duct 5. The lower end of the guide rod 33 is screw threaded to receive the elongated nut 34` extending through the lower wall of the air duct and provides a manually adjustable stop to limit. the downward movement of the weight-32. The free end of the plate 3l `is formed with an open slot 35 to receive the guide rod 33 and this slot is also of suicient width to prevent contact of the plate with the upper end'of the stop nut 34.

The bottom wall of the air duct 5 is curvedupwardly adjacent the guide rod 33as indicated at 36 in Figure 2 for a purpose'to be hereinafter set extending outside :of one' upper hooked end of a tensionY plate I2 is pivotally supported adforth, and a portion of the side wall of the air duct is cut away adjacent the damper to provide an inspection opening which may be normally closed by the plate or cover 3'I mounted to slide in the vertical guides 38 with the upper edge of said plate or cover bent outwardly to provide a flange 39 thereon to limit downward movement of the cover by contact with the upper ends of the guides 38 and afford means to grasp said cover to open or remove the same when desired.

Proceeding now to a description of the operv ation, it has been stated that the damper mechanismis` adapted to automatically regulate the air now. in the air delivery duct from the fan or blower to the fuel bed in accordance with the fvariations inv the resistance to the flow of air through the fuel bed.

It may be generally stated that the operation of the damper to change the volume of air which may pass through the duct is primarily regulated by the velocity of the air in the `duct which will vary in accordance with the back pressure caused by the fuel bed resistance. The static pressure in the duct between the damper-and the fuel bed is a function of the velocity of the-air flow and the resistance interposed by the'fuel bed and it is desired to obtain by the damper a substantially linear change in the volume of air with the linear change of static pressure.

Referring now to Figure 2, the damper/9 has been shown in full lines in the idle position which is assumes when adjusted for a high rate of coal feedy in which the maximum volume of air may flow-through the duct to the fuel bed. In order to obtain effective regulation, this maximum volume of air is equal to or in excess of the amount that would be required at any-time, and as will be explained hereinafter, the damper will roll on the fulcrum plate I24 and occupy some position during normal operation which is between the full line position and that shown inv dotted lines in which substantially the minimum volume of air may flow through the duct to the fuel bed. Y

It will rst be apparentV that the adjustable tension spring 28 exerts a force tor hold the damper in the idle position when the Stoker feed screw and blower are not operating and offers a regulatable resistance to closing of the damper duringV operation of such stoker mechanism. The anchorage end of the spring 28 is so located as to position such spring at an acute angle to the longitudinal axis of the damper 9, and this angle is such, in relation to the variable fulcrum, that the ultimate result of the damper movement is to maintain a substantially constant torque arm on the damper and provide resistance to closing of the damper which increases by the stretch of the spring only.

The effective length of the spring arm is represented by the dotted line A in Figure 2, and it will be seen that the spring 28 can be so placed with reference to the fulcrum plate I2 that this length A is substantially constant over the working range of the damper. If the spring 28 was, for example, anchored at a point so that a greater angle was formed between the axis of the spring 'and the upper surface I8 of thedamper, the length' of A would increase as'the damper closes. kWhile it has been found that for application to domestic coal stokers the length of A should be maintained reasonably constant, conditions may arise onother applications where it wouldbe desirable to have the length of A or the effective length of the springarm increase or Adecrease .as the damper Vcloses lwhich may zreadily be fachieved ;by changing the .anchorage -point of l the .spring :28.

'To provide 'for the proper operation -of :the damper by the air forces in the manner thereinafterdescribed, yit is necessarythat .theinitial tension of 'the spring vbe just sufficienttoovercome vthe force 4exerted i by l.the damper .and :hold the damper .in Vthe idle positionshown in full lines in VFigure 2. If .nofweight r(such as $32) is provided, Vthe initial tension of the spring 128 would have to be so low thatthe damper Awould be subject to oscillations of a'high periodsand to hunting or flutteringbecause of the practically frictionless mounting `of the damper on the curved fulcrum kplate I2.

Such hunting or fluttering would arise if the damper momentarily over-shoots its normal operating position at any time such as would oc- -cur on a sudden movement of the damper when its inertia would carry it past its normal operating position thereby storing extra energy in Vthe spring 28 which would cause a movement in the reverse direction past its normal operating `position and the resulting lsurges in the air flow would tend to sustain this hunting or fluttering of the damper.

To overcome this unstable condition, the weight 32 is provided to exert a force tending to .close the damper and permit an increase in the initial tension of spring 28 and thereby reduce 'the periodicity of the damper oscillations, vand this weight 32 is so mounted as to function also asa dampening means to prevent hunting or fluttering.

If the weight 32 were attached directly to the damper its only effect would be to reduce the periodicity of the oscillations and the damper would still be unstable and subject to hunting or uttering. The weight is, however, mounted as shown to slide vertically on the guide rod 33 `and rest upon the damper extension plate 3l, and the friction which is thereby introduced between the weight 32 and the guide rod 33 and between the weight and the plate 3| functions.

todampen out and prevent this hunting o"r fluttering of the damper. Since the weight 32 is free to move independently of the damper 9, it also does not respond to the same frequency and thus .acts to dampen out any oscillation or hunting action.

It has been found desirable to relieve the -damper of any controlling force from the weight 32 when the damper approaches its lowest position and the adjustable stop nut 3ft is adapted to engage and limit the downward movement of `the weight32 while permitting continued closing movement of the damper until it contacts with thewalls of'the air duct 5. With the force exerted by the weight removed by the engagement of the weight 32 with the stopnut 34, it ywill lbe seen that the downward motion of the damper l9 will be rapidly checked by the spring 28.

Considering now the air forces acting on the damper which are adapted to automatically regulate .its position in accordance with the resistance offered by the fuel bed, it will `rst be noted lthat the air flow in the air duct 5 is in the direction-indicated by the arrow in Figure 2. The

damper 9 is of generally airfoil shape and the i movement thereof about the curved fulcrum lplate l2 is a result of the reaction on its surfaces of the air flow through the air duct.

The curved lower surface H of the damperis :so Aarranged with reference to .the .upwardly .curved portion35 ofthe air .duct '-5 as to :form -a 'Venturifpassage 4Q 'between .the 1damperand the bottom '.Walllofthe air vduct which Vfunctions to exerty a suction or vacuum tending .tovpull the damper downwardly Vor-in. a direction ;to.close.the airduct. The. suction forcefexertedby thisVenturi action .varies in accordance withzthe air velocity and the area of the Venturi passage. The air velocity is determined .by the vresistance of the fue1:loed. When thefuel bed is thick .theair velocitywilllbe `lowand thesuction elf-ect of the ,venturi will below. .When `,the fuel bed .is thin fthe air vvelocity-.will be .highland the-suction ef- '.fect .will be high which .will tend zto close ithe .damper .rand reduce the area of :the Venturi `passage 14,0,'2.which in `turn reduces :thetotal vvolume -o'f air which .may pass through :this passage.

This "Venturi :action is however not `sufficient to operate the damper J.and is supplemented-by .the application of .l air .pressure :above =the damper. .In the ypositionvof` the damper Ashownin ifull lines .in Figure 2, the a'ir flow Ais divided by the'damper into two vpaths with ythe air .flowing throughthe `Venturi :passage .'4'0 below the damper .and :through .a .passage 1i l =between .the upper surface Y'Ill ofthefdamper and the upper .wall .of ;theair duct. .The air :which flows fthroughthe :passage il passes `through the .Nl-shaped notent-6 in fthe wall '-24 and-the amount of air iiow throughthis passage and therefore the pressure differential between-the tcp-,andbottomvof the damper will be determined'by the sizeof this notchl'ZvS. 'It has .been heretofore noted that the wall .2'3 on the damper functions asa valveacross thewall v24.and it will be apparent that the eifectiveiarea Yof 'the notch l26 duringoperationiwilllbe dependnent upon: the p'osition of the damper,..and thatas the damper moves .infa vdirection to reduce the lsize of the Venturi passage 46, the area ofthe notch -will'also be `reduced y-to llower-the volume of air flow through the passage 11|.

"The -ai-r flow inthe passage M exerts a pressure on the upper surface l0 offthe damper which, :in -efect,fmayibe divided into 'two components, :acting in oppostionto one :another onopposite sides of the fulcrum point of the damper onvthe -curved fulcrum plate -|2. 'The air pressure acting on that portion of the damper surface vIllbetween the fulcrum-point andthe-end of the-dam.- 'per `'with the wall A23 exerts an opening .force or a force 'tending to rotate the damper fin -a :counter-clockwise direction and open the damper, whereastheair pressureacting on that portion-of the damper surface I' `between y'the fulcriun point and -theend of thefdamperwiththe platef3l exerts a closing force or a force tending to rotate the damper in a clockwise direction and close the damper. The relative magnitudes of vthese components, acting as opening andclosing forces on the fdamper, are dependent upon l'the relative A'areas of the damper surface ID on eachside of the fulcrum point.

As will'be apparent from the-.showing inFigure `2, the fulcrum `of ther damper'is closer'to one -end ofthe damper-when in its full line position -so that the closingforce isgreaterrthan the opening force, but the fulcrum shifts during closing movement of the damper towards the longitudinal center of the damper resulting inran increase in thefopening `forcefand a decrease inthe closing force until such forces are substantially balanced when the damper is practically closed.

vsummarizing the several forces acting on 'the damper, itwillfbeseen that both the rspring 2,8 sandtthe air pressurezon thaupnerfsurfacezc the damper between the fulcrum point and the end of the damper with the wall 23 exert forces tending to open the damper, whereas the dampening weight 32, Venturi passage 40, and the air pressure on the upper surface of the damper between the fulcrum point and the end of the damper with the plate 3l exert forces tending to close the damper.

These several forces are so related and proportioned that when the fuel bed is relatively thick and offers a high resistance, the relatively low velocity of the air ow through the air duct will cause only a slight closing movement of the damper from the idle position and permit the ow of a relatively large volume of air (which is in excess of the volume of air normally required) through the passages 40 and 4I to thereby increase the normal rate of combustion and reduce the thickness of the fuel bed.

If, however, the fuel bed is relatively thin and offers only a slight resistance, the relatively high velocity of the air flow through the air duct Will act on the damper to close the passages 4B and 4| to such an extent that a deficient volume of air will be supplied to the fuel bed to reduce the normal rate of combustion and thereby permit the fuel bed to increase in thickness.

The damper will adjust itself automatically during operation in response: to changes in the velocity of the air flow in accordance with changes in the thickness of the fuel bed to permit the supply of that volume of air which will tend to establish and then maintain the fuel bed at the desired thickness.

Various adjustments are provided to change the automatic operating characteristics and the range of operation to adapt the damper operation for variations in the quality of the fuel or changes in the rate of fuel feed. The principal adjustment is afforded by the damper handle l1 by means of which the eccentric or cam l5 may be rotated to Vary the position of the fulcrum plate I2 about the pivot shaft I4. In the damper position shown in full lines in both Figures 2 and 5, the cam l5 is adjusted for a high rate of coal feed, whereas in Figure 5, the cam l5 is shown in dotted lines as having been rotated to permit the fulcrum plate l2 to assume a lower position for a loW rate of coal feed in which the damper would assume the idle position shown in dotted lines in which it is partially closed. It will also be seen that rotation of the cam I5 and the resulting change in position of the fulcrum plate l2 will change the fulcrum point of the damper and thus vary the relative pressures acting on the damper on each side of the damper fulcrum.

A further adjustment is afforded by the adjustability of the tension of the spring 28 to change the force of this spring which opposes the closing movement of the damper under the inuence of the velocity of the air flow in the air duct. It will also be apparent that the shape or size of the V-shaped notch 25 can bek modied to change the volume of air which may flow through the passage 4| and change the pressure differential between the top and bottom of the damper.

Whereas the automatic air control mechanism of the present invention was designed for use in a domestic underfeed stoker for intermittent operation and has been so illustrated and described herein, it should be understood that the invention is not limited to this particular use but may be generally used with other types of heating devices wherein it may be desired to automatically regulate a forced draft in accordance with the resistance of the fuel bed, or it may be used to control the fluid ow 'in the duct of any forced draft system.

It will also be understood that the invention is not to be limited to the details of the mechanism of the single embodiment illustrated and described herein but that many modifications and changes may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim:

1. The combination with a duct for conveying air under pressure, of means to regulate the volume of air iiow through said duct comprising a damper in said duct, a curved plate to support said damper intermediate its ends and provide a shifting fulcrum therefor, and manually adjustable means to change the position of said curved plate and the fulcrum point of the damper thereon.

2. The elements set forth in claim 1 in which said curved plate is pivotally supported adjacent one end, and said adjustable means comprises an eccentrically adjustable support for the opposite end of said curved plate.

3. The combination with a duct for conveying air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, means supporting said damper intermediate its ends, a spring co-nnected to one end of said damper and exerting an opening force thereon, and a Weight acting upon the opposite end of said damper and exerting a closing force thereon, and means to mount said Weight arranged to provide sliding frictional resistance to changes in the position of said damper.

4. The combination with a duct for conveying air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, means supporting said damper intermediate its ends, a spring connected to one end of said damper and exerting an opening force thereon, and a weight engaging the opposite end of said damper and exerting a closing force thereon, a guide rod on which said weight is mounted to slide vertically, and an adjustable stop on said rod to limit the downward movement of said weight.

5. The combination with a duct for conveying air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, the bottom surface of said damper being downwardly curved and the bottom wall of said duct being curved upwardly at a point opposite said damper to provide a Venturi passage between said damper and said bottom wall.

6. The combination with a duct for conveying air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, said damper being generally of airfoil shape with converging upper and lower surfaces and adapted to assume various positions of adjustment as a result of the reaction on its upper and lower surfaces of the air flow through the said duct.

7. The combination with a duct for conveying air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, means providing a fulcrum support for said damper intermediate the ends thereof which is variable on movement of said damper, and means to restrict the free flow of air through said duct between said damper and one of the walls of said duct whereby the air pressure therebetween will exert opening and closing forces, respectively, on the portions of said damper on opposite sides of the fulcrum point thereof, and which portions will vary in relative extent during movement of said damper on said variable fulcrum support causing thereby a relative change in the said opening and closing forces.

8. The combination with a duct for conveying air under pressure to the fuel bed in a combustion chamber, of a damper in said duct, means providing a fulcrum for said damper intermediate the ends thereof and intermediate the upper and lower walls of said duct which is variable on movement of said damper, a spring connected to one end of said damper to exert an opening force thereon, a weight engaging the opposite end of said damper to exert a closing force thereon, a Venturi passage formed between said damper and the lower wall of said duct whereby air flow through said passage exerts a closing force on said damper, and means to restrict the free flow of air through said duct between said damper and the upper wall of said duct whereby the air pressure therebetween will exert opening and closing forces, respectively, on the portions of the upper wall of said damper on opposite sides of the fulcrum point thereof, whereby said damper will function the volume of air fiow through said duct in accordance with the resistance of the fuel bed.

9. The combination with a duct for conveying Jair under pressure, of means to regulate the Volume of air flow through said duct comprising a damper in said duct, and means providing a fulcrum for said damper which is variable on movement of said damper, and a spring connected to one end of said damper and exerting a force opposing the closing movement thereof, said spring being so mounted with reference to said damper and the variable fulcrum thereof as to maintain a substantially constant torque arm on said damper during the movement thereof.

10. The combination with a duct for conveying air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, means supporting said damper intermediate its ends, a spring connected to one end of said damper and exerting an opening force thereon, and a weight engaging the opposite end of said damper and exerting a closto automatically regulate ,l

ing force thereon, said weight being mounted to slide vertically on a guide rod and merely resting upon said damper whereby said weight functions effectively as a dampening means to prevent hunting or fluttering of said damper during changes in the position thereof.

11. The combination with a duct for conveying air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, means supporting said damper intermediate its ends, a spring connected to one end of said damper and exerting an opening force thereon, and a weight engaging the opposite end of said damper and exerting a closing force thereon with means to limit the movement of said weight and relieve the damper from the force exerted thereby when the damper closes a predetermined extent.

12. The combination with a duct for conveying .air under pressure, of means to regulate the volume of air flow through said duct comprising a damper in said duct, means supporting said damper intermediate its ends and intermediate the upper and lower walls of said duct, and means adjacent one end of said damper to restrict the free passage of air through said duct between said damper and one of the walls of said duct, said last-named means comprising a wall extending across a portion of said duct adjacent one end of said damper with an opening in said wall for the passage of air, and Vsaid damper being provided with an end wall which is adapted to vary the size of said opening during movement of said damper.

13. The combination with a duct for conveying air under pressure, of means to vary the volume of air ow through said duct comprising a damper in said duct, means for mounting said damper in said duct in spaced relation to opposite walls thereof so that opposite sides of said damper are exposed to air passing through said duct, said mounting means including a fulcrum for said damper intermediate the ends thereof which is variable on movement of said damper, and said damper being so constructed as to move on said fulcrum in accordance with changes in air velocity in said duct.

14. The elements set forth in claim 13 in which a spring is connected to one end of said damper to exert a force opposing the closing movement thereof.

WILBUR L. CARLSON. 

